The compound with the structure outlined below is presently in clinical trials for Parkinson's disease (Idrugs, 2003, 6(4), 377-383).

This compound is in the following referred to as Compound I. The chemical name of Compound I is [9S-(9α,10β,12α)]-5,16-Bis[(ethylthio)methyl]-2,3,9,10,11,12-hexahydro-10-hydroxy-9-methyl-1-oxo-9,12-epoxy-1H-diindolo[1,2,3-fg:3′,2′,1′-kl]pyrrolo[3,4-i][1,6]benzodiazocine-10-carboxylic acid methyl ester.
The following references relate to Compound I, in particular to methods for its preparation [J. Med. Chem. 1997, 40(12), 1863-1869; Curr. Med. Chem.—Central Nervous System Agents, 2002, 2(2), 143-155] and its potential medical uses, mainly in diseases in the central nervous system (CNS), in particular for treatment of neurodegenerative diseases, e.g. Parkinson's disease, Alzheimer's disease, Huntington's disease, peripheral neuropathy, AIDS dementia, and ear injuries such as noise-induced hearing loss [Progress in Medicinal Chemistry (2002), 40, 23-62; Bioorg. Med. Chem. Lett. 2002, 12(2), 147-150; Neuroscience, Oxford, 1998, 86(2), 461-472; J. Neurochemistry (2001), 77(3), 849-863; J. Neuroscience (2000), 20(1), 43-50; J. Neurochemistry (2002), 82(6), 1424-1434; Hearing Research, 2002, 166(1-2), 33-43].
The following patent documents relate to Compound I, including its medical use and synthesis: WO 9402488, WO9749406, U.S. Pat. No. 5,621,100, EP 0651754 and EP 112 932.
By the known methods, Compound I is synthesized in a solid amorphous form. The inventors have now discovered 5 crystalline forms of Compound I (named alpha, beta, gamma, delta and epsilon) thereby providing an opportunity to improve the manufacturing process of Compound I and its pharmaceutical use. There exists a need for crystalline forms, which may exhibit desirable and beneficial chemical and physical properties. There also exists a need for reliable and reproducible methods for the manufacture, purification, and formulation of Compound I to permit its feasible commercialisation.